Henry wtjbtz



UNITED STAT S PATENT OFFICE.

HENRY WURTZ, on NEW YORK, N. Y.

PROCESS OF TREATING MINERAL PYRITESAND SULPI-IIDES FOR THE MANUFACTURE OF SULPHUROUS AND SULPHURIC ACIDS.

SPECIFICATION forming part of Letters Patent No. 252,287, dated January 10, 1882. Application filed April 11, 1881. (Specimens) Patented in Canada October 1, 1881.

To all whom it may concern c Be it Known that I, HENRY WURTZ, of the city of New York, county of New York, and State ofNew York, have invented an Improved Process of Treating Mineral Pyrites and Sulphurets in the Preparation therefrom of Sulphurous and Sulphuric Acids, of which the following is a specification.

This invention is especiallyand directly applicable to minerals composed of sulphur with iron or copper, or with both these metals to gether, including common yellow-iron pyrites, yellow-copper pyiites, white-iron pyrites, or marcasite magnetic pyrites, or pyrrhotine, or mixtures of any of these, or mixtures of these with other minerals or ores, when such sulphu{ rets occur in a pulverulent, comminuted, or granularstate, whether found naturally in such granular state or as reduced incidentally to such state by handling or transportation, or when pulverized by artificial means, either purposely or incidentally, as in the case of con- -centrated sulphurets or tailings from ore-milling operations.

The invention consists, first, in mingling with such pulverulent or granular sulphnrets metallic iron, also in granular or com minuted, state,and moisteningthe mixture with a saline solution, which will cause theiron to rust, and thus cement the granules together into a coherent mass; second, in aiding and accelerating the rusting of the iron in such mixture, and thus hastening the consolidation thereof, by an alternating application of heat and moisture.

-When sulphurets are to be operated on which occur in a compact or massive form it is necessary in the application thereto of this invention to crush them previously to a granular or powdery conditioin,

The crushing of the pyrites or other ore may, for the purposes of this invention, be acconiplished by the ruder and more rapid methods, and thus without expensive plant, for the reason that it is not essential that such crushing should beuniformly fine. The tinerand coarser material should, however, for reasons well known to those skilled in the art of cot-centrating ores, be sorted or separated by screens of difi'erent'apertures into fractions or sorts of more uniform sizes of granule respectivelyprocess of concentration has been applied.

This is because a certain proportion of powder of a considerable degree of fineness is requisite to fill up the interstices between the larger granules, in order to promote compactness in the mixture to be consolidated. This proportion of fine material varies generally from onehalf to threefourths of the whole, according to the size or degree of coarseness, as well as the shape also of the coarser particles, the size to which it is advisable to reduce the latter being dependent on the variable degree of crushing needed with different ores to free the sulphuret from the gangue sufficiently for the concentration process. The proportion of finely-screened to coarser material with any special ore is therefore best determined by tentative experiments. When thus ascertained such proper proportion can be uniformly insured by dint of the sortingand sifting of the crushed ore previous to concentration, which is recommended above.

The mixing ofthe fine and coarse sorts ot'concentrated sulphuret in proper proportions with each other, and with the granulariron and the saline solution, together with abestus or mica, il'eniployed, may be effected by hand-tools, or by any kind of common rotary mixing-machine,

but it has been found important that the saline solution should be heated nearly to its point of ebullition, and that the granulated ore, with the granular iron, &c., be also previously and uniformly heated to or near the temperature of boilingwater, which is rapidly accomplished 5 by passing hot air through the mass, whether the latter be dry or moist. The air, driven by a small rotary blower or otherwise, passes first through a coil immersed in boiling-hot water, and then into a chamber forming the lower part of a receptacle containing the fine and coarse sorts, together with the granular iron, &c., the components havin gbeen roughly mixed by fractional shoveling in the operation of filling the receptacle. This partial mixture rests on a diaphragm of fine wire-gauze, supported by a coarser iron grating, this diaphragm forming the ceiling of the inferior chamber aforesaid, from which chamber the hot air percolates upward through the diaphragm and its superposed mass.

When it is desirable to operate directly on wet granulated pyrites as these come from the concentrating apparatus, without draining or drying, for the sake of saving time, or other reason,-and if the mass be too much clogged with moisture to allow of the percolation of the heated air, the above apparatus may, by the employment of a reversible blcwer be used for first extracting the excess of moisture by creating first a diminished pressure in the inferior chamber. The blower being after this reversed, and the hot air turned on, the heating operation ensues. After becoming heated throughout, the granular mass is then introduced by means of elevating-buckets into the mixing box or vat, together with a properlyproportioned stream of the boiling-hot saline solution. Thecompletcdmixture,which should have about the consistence of thick mortar, is spread in a thin layer of from half an inch to an inchpreferably about three-fourths of an inch-upon square thin sheets of lead, which are supported and transported on light and thin movable iron gratings or hurdles. A square wooden frame-work or rim is temporarily'applied to the sheet of lead to confine the mixture. When the latter has been sprea'd uniformly this frame may be removed and the hardening process then proceeded with, the large cake thus obtained being broken subsequently by hand into fragments of suitable size for the kiln. The-following plan, however,

is preferable: An inverted mold is provided, composed of cast-iron, tinned superficially to prevent rusting, which mold is so constructed with knife-edge septa as, when brought down over the cake of mixture and applied thereto with adequate pressure, to cut down into and divide the sheet or cake uniformly nearly through its whole thickness into square, triangular, or preferably hexagonal segments or disks each of about three or four square inches superficial area, in a manner similar to that of the handling of dough by a biscuit cutting or molding machine. The sheet of lead, with its charge of composition, supported by its iron grating, is then laid side by side with others on a metallic table having an inclosed space below,which may be heated by hot air or steam to a temperature of from 120 to 150 Fahrenheit. Arrangements are also provided by means of which water, as a shower of very finely divided atomized spray, may be sprinkled uniformly over the surface of the mixture when so desired. The further process consists then in alternately sprinkling the porous mixture very uniformly and gradually with water till permeated and moistened throughout, and

allowing it to dry slowly, either by spontaneous evaporation or under the influence of a very gentle heat applied from below, as already explained. From four to six alternations of the wetting and drying operations, occupying, according to the proportion and fineness of division of the granular iron in the mixture, as well as to the tem perature applied, from twenty- 'four to forty-eight hours, effects the complete consolidation of the mass. The sheet of lead is then,by bending, readily separable from the consolidated cake, and the latter, by virtue of the segmental divisions made while soft, as above described,is readily divisible'into'disks of uniform size, ready for burning in the pyrites-kiln.

The granular iron used in this process may be of any commercial variety of granulated metal, either borings, turnings, planings, or filings, either of foundry-pig or other pig, wrought-iron, low steel, Bessemer, or other ingot-iron. It is usually desirable that'it be free from such impurities as would contaminate the cinders for any special uses to which the latter are to be applied. Thus, for exemplification, if the cinders or residues in the kiln are to be used'in making Bessemer pig or openhearth steel by a pig-and-ore or a pig-andsponge or other process, orif, again, amalgamation or chlorination is to be applied to them for extraction of gold, the granular iron used ought, in the first case, to be tolerably low in phosphoi us, and in both the first and second cases it ought to be previously put through a magnetic separator to eliminate all incidental lead, zinc, copper, and brass, with rags, sawdust, sand, and other non-metallic impurities. If grease be present in the granular iron, it should be lixivated previous to use with dilute caustic soda or with petroleum-naphtha. 1f the sat phurets operated on be cupriferous, and copper is to beextracted from the cinders, of course the presence of copper and brass in the granular iron may be neglected.

If it be necessary to use granular iron as presented in commerce, it should be procured, if practicable, solely from operations or establishments Where sol't foundry-pig or castings thereof are bored or finished, for the reason that fineness of division of the iron is conducive to much economy of time in operating this invention, and such soft borings or planings are easily reducibleto veryfine division, at least in great part, by first pounding under chilled-iron stamps and then grinding in mills having bearing-surfaces of hard chilled iron or spiegel-iron.

Pig-iron may also be finely granulated, for the purposes of this invention, by the centrifugal method of the Baron de Rostaing, by passing melted pig in a small stream through a funnel placed over the center of a horizontal whirlingcast-iron table making two thousand revolutions-per minute; but the form of comminuted iron which I have found preferable for thepurposes of this invention is that known commercially as iron sponge, produced by the deoxidation oi previously-pulverized iron oxide, at temperaturestoolow to weld or agglomerate together the granules of reduced metal. If, however, iron sponge'be purchased for the uses of this invention, assurance should be obtainedby' analysis that it has been pre pared from an ore previously freed from gangue, and not contaminated with impuritiessuch as phosphorus, &c.-which will detract from the value of the residues for rneta-llurgi' cal or other purposes. Above all, such sponge must have been deoxidized with'at least approximate completeness -'-that is, must be nearly freefrom intermixed unreduced oxides of iron, whichlatt'er are wholly-inert for the purposes of this invention.

ltistobepointedoutthatthecinderorresidue resulting from the burning of purified iron pyrites thathavc been prepared orcaked by this invention is highly and especially suitable for the preparation of iron sponge to housed in carr lug out the invention itself. t It is to be noted, likewise, that all the metallic iron employed f or the purpose of consolidation according to this invention being recovered again in the form of oxide which adds itself to the cinders, the cost of such iron used in carrying out this process is reduced to a much lower figure.

The saline material employed in carryingout this process for causing rapid rusting of the granular iron under atmospheric influences must, first, be neutral or tree from sufiicient acidity to give rise to any evolution of hydro gen from action on the iron, as I have found such gaseous evolution in the mass to be highly objectionableby producing porosity, and thus diminishingcohesion. Secondly, deliquescent salts, like the earthy chlorides, are also highly objectionable, as interfering with the method set forth of accelerating oxidation by a1terna tions of drying and moistening. Such chlorides as common salt and sal-ammoniac, even though not themselves deliquescent, are likewise inadmissible, as they lead to the formation of the highly deliquescent sesqui-chloridc otironinthemass. Thirdly,anotherconclusive objection to all chlorides is that if applicable they would have tobe washed out of the mass again after consolidation, or otherwise the solphurous oxide proceedingfroin the pyrites-kiln and the oilof vitriol resulting therefrom in the acid-chambers would be contaminated with muiiatic acid. Fourthly, highly eftlorescent salts-as, for instance, sulphate of soda-cannot be used, eftlorescence proving almost as much in the way of the alternating method of oxidation as the opposite quality of deliquescence.

As saline agents, I have forthe above reasons found it necessary to employ certain sulphates, and of these common sulphate of iron-green vitriol, or coppera-s-preseuts,with great cheapthan this it may be cut down.

mess and c011 venien ce, the highest adaptability on the Whole, though the sulphates ot'magntesia and zinc have been found to possess superior consolidating power,-aud sulphate of alumina has alsobeen foundapplicable. Sulphate of copper maybe present without detriment. Sulphates of potash and ammonia, though found effective, are too expensive for ordinary use. Where magnesian minerals soluble in snlphu-' ric acid, like serpentine and 'magnesite, are cheaply obtainable, a solution of crude sulphate of magnesia may be prepared and applied to advantage for these purposes. Sulphate of zinc is liable to the important olnjection that it is not readily decomposed by the heat of burning pyrites, and its sulphuric acid remains accordingly to contaminate the cinder. Sulphates of magnesia and alumina are decomposable by the heat of the kiln. Sulphate of iron is also completely decomposed in the kiln, and as the products of such decomposition are solely iron oxide with sulphurous and sulphuric'oxides, all of which are utilized in the process, it may be said that sulphate of iron is, for the purposes ofthis invention,virtually without cost, except for labor in handling, 850,

Asbestus,\vhich I mingle when desirable with the sulphurets tobe consolidated, tor the purpose of divesting the resulting cinders of all tendency to crumble, either in the kiln or in subsequent handling, may be of coarsestand cheapest quality and of short fiber, onehalf inch being sufficiently long, though somewhat longer fiber is sometimes preferable up to one inch, beyond which little or no advantage canarise; audit the staple be longer Dark or rusty color is, of course, no objection for these purposes. The fiber should not be carded or separated too completely or finely, so as to diminish the average strength of the single fibers too much, a mean fineness being generally preferable in this case.

Mica,'which I also sometimes use for the same purpose for adding cohesion to the mass during and after the action of the kiln, may be very cheaply obtained for the purposes of this invention by disintegrating mechanically many abundant mica-schists, with or without subsequent wasliin g to separate t he mica-scales from quartzose or other impurities. Such mica maybe cut, if preferred, into narrow elongated ribbons, which need not be more than halt an inch in length.

t The proportions of the agents and materials used for consolidation of granular sulphurets by this method admit of a certain amount of variation. When the metallic iron used is clean and very finely comminuted, as in the form of fine filings, fine sittings from ground borings of cast-iron, or well reduced iron sponge, five per cent. of the weight of the sulphurets to be consolidated yields results as good as any, and

there is usually little or no advantage in the use Igo or cleanliness, it may be advantageous to increase the proportion up to seven, eight, or even, in extreme. cases, ten percent. The amount of protosulphate of iron admissible, taking it as commercial crystallized green vitriol with seven equivalents of water of crystallization, is generally five per cent. of the weight of the sulphurets. 'This is the maximum that is admissible without detriment to the process, such detriment arising mainly from crystallization of the green vitriol in the superficial pores of the cake undergoingconsolidation, which diminishes the coherence of the superficial granules. With good manipulation three per cent. of green vitriol gives good results; but because, as before stated, the constituents of the,

green vitriol are recovered in forms even more valuable than itself, there is probably no important advantage in using less than four or five per cent.

The amount of asbestos that I have used to effect good results therewith has been one per cent. of the weight of the snlphurets; but twice this proportion may be used to advantage if cheaply obtainable. Mica in thin scales may be used to the extent of two or three per cent. or even more, being very cheaply obtainable.

Great advantages and economies in the manufacture of sulphuric acid from sulphurets arise out of this mode of previous preparation of the ore. The porous solid material thus obtained kindles much more readily and propagates its own combustion, such combustion being much more rapid, complete, and uniform than with compact lump pyrites, so that less than one per cent. of sulphur is left in the cinders, the kilns requiring also much less attendance and less of expensive skilled labor than in the usual Way. The cinders or residues will also be found much more available for all purposes to which they are applicable.

I am aware that granular pyrites have been cemented with clay into blocks which could be imperfectly burned in kilns, and also that by 5 a method in use of late in Europe pyrites pug-mills to-a mud, which, in the case of some varieties of pyrites, when molded into cakes,

. hardens by drying or slight baking sufficiently to be handled and burned in kilns. In my method, however, the consolidation does not arise from any cohesion set up by oxidation or otherwise, or from any other change of the snlphurets themselves, but is effected by the agency and through changes of other materials added thereto, which act independently ofthe special characterof the snlphurets themselves and on all varieties alike. Ido not there-- fore claim, broadly, as a novel invention the agglomeration of granulated snlphurets; but

What I do claim is- 1. The consolidation of granular snlphurets before burning in kilns to make sulphurous or sulphuric acids into cakes, lumps, or blocks by mixing therewith metallic iron in comminuted or divided form, and causing this iron to rust and form hydrated oxide or a basic salt in the interstices of the mass by mixture with a saline solution.

2. Accelerating and intensifying the rusting and cementing action of metallic iron when mingled with granular snlphurets to be burned in kilns for making sulphurous and sulphuric acids by the process of alternately moistening the mixture with water and drying, either spontaneously or by a gentle heat, as herein specified. I

3. As a new product or com position of matter to be used in making sulphurous and sulphuric acids by burning the same in kilns, a consolidated product made by mingling together granulated metallic snlphurets with granulated metallic iron, asbestus, or mica,

and in which composition oxidation or rusting has been produced by the action of a saline solution, as herein described.

HENRY WURTZ. Witnesses:

AUSTIN GALLAGHER,

EDWIN BOLITHO. 

